Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$122.94	7.262%	$131.8679	$131.87	$131.85	$131.90
Purchase #2	$88.62	13.308%	$100.4135	$100.41	$100.40	$100.40
Purchase #3	$206.67	10.751%	$228.8891	$228.89	$228.90	$228.90
Purchase #4	$179.45	11.771%	$200.5731	$200.57	$200.55	$200.60
Purchase #5	$111.65	4.541%	$116.72	$116.72	$116.70	$116.70
Purchase #6	$101.45	10.497%	$112.0992	$112.10	$112.10	$112.10
Purchase #7	$205.65	13.671%	$233.7644	$233.76	$233.75	$233.80
7 purchase totals =	$1,016.43		$1,124.3272	$1,124.32	$1,124.25	$1,124.40